Patrick Vallance
Synopsis
• Preclinical drug development. Discovery of new drugs in the laboratory is an exercise in prediction. Selecting the target for a drug is probably the key decision.
• Techniques of discovery. Several approaches, including using small molecules, large proteins and nucleic-based approaches, broaden what we think of as a medicine.
• Studies in animals. Some are required by regulation (for safety), others give insight into the effect of the drug in the whole body, but none replaces the need for clinical testing.
• Experimental medicine. Getting the medicine into the clinic to test its properties and its effects on biological systems is a key step.
• Ethical issues.
• Need for animal testing.
• Prediction. Failures of prediction occur and a drug may be abandoned at any stage, including after marketing. New drug development is a colossally expensive and commercially driven activity.
• Orphan drugs and diseases.
Making a new medicine
Discovering and developing a new medicine requires combining the skills of biology, chemistry, clinical medicine and, of course, pharmacology. There are three key decision points along the way:
1. Selecting the molecular target you want the drug to act on to produce the desired effect.
2. Choosing the right chemical as the drug candidate. All the promise and all the faults become fixed at this point.
3. Designing the right clinical experiment to show that the medicine will really do what you want it to do.
Medicinal therapeutics rests on the two great supporting pillars of pharmacology:
1. Selectivity – the desired effect alone is obtained: ‘We must learn to aim, learn to aim with chemical substances’ (Paul Ehrlich).1
2. Dose – ‘The dose alone decides that something is no poison’ (Paracelsus).2
Once a target has been selected the process of finding the right chemical to act as an antagonist, agonist, inhibitor, activator or modulator of the protein function depends on a process of screening. For decades, the rational discovery of new medicines depended on modifications of the structures of natural chemical mediators. This may still be the route to find the drug, but more often now large libraries of compounds are screened against the target in robotic high throughput screens. However, it is worth remembering that the exact molecular basis of drug action may remain unknown, and this book contains frequent examples of old drugs whose mechanism of action remains mysterious. The evolution of molecular medicine (including recombinant DNA technology) in the past 30 years has led to identification of many thousands of potential drug targets, but the function of many of these genes remains unknown. The hope was that the identification of targets identified by genetics coupled with high throughout screening would lead to a great increase in the productivity of drug discovery. This has turned out not to be the case since it is clearly important to understand both the function of the target and the nature of the interaction of the chemical drug with the target in order to make a selective and safe medicine. The skills of quantitative pharmacology are key.
The chances of discovering a truly novel medicine, i.e. one that does something valuable for patients that had previously not been possible (or that does safely what could previously have been achieved only with substantial risk), are increased when the discovery and development programme is founded on precise knowledge of the biological processes it is desired to change. The commercial rewards of a successful product are potentially enormous and provide a great incentive for developers to invest and risk huge sums of money. Most projects in drug discovery and development fail. Indeed the chances of making it through from target selection to having a medicine on the market are under 1 in 100.
The huge increase in understanding of molecular signalling – both between cells and within cells – has opened many new opportunities to develop medicines that can target discrete steps in the body's elaborate pathways of chemical reactions.3 The challenge, of course, is to do so in a way that produces benefit without harm. The more fundamental the pathway targeted the more likely there is to be a big effect, whether beneficial, harmful or both. No benefit comes without some risk.
The molecular, industrialised and automated approach to drug discovery that followed sequencing of the genome and application of high throughput chemical approaches led to two consequences:
1. More potential drugs and therapeutic targets were identified that could be experimentally validated in animals and humans. This ‘production line’ approach also led to a loss of integration of the established specialities (chemistry, biochemistry, pharmacology) and to an overall lack of understanding of how physiological and pathophysiological processes contribute to the interaction of drug and disease.
2. Theoretically, new drugs could be targeted at selected groups of patients based on their genetic make-up. This concept of ‘the right medicine for the right patient’ is the basis of pharmacogenetics (see p. 106), the genetically determined variability in drug response.
Pharmacogenetics has gained momentum from recent advances in molecular genetics and genome sequencing, due to:
• rapid screening for gene variants
• knowledge of the genetic sequences of target genes such as those coding for enzymes, ion channels, and other receptor types involved in drug response.
Expectations of pharmacogenetics and its progeny, pharmacoproteomics (understanding of and drug effects on protein variants) remain high, but the applicability will not be universal. They include the following:
• The identification of subgroups of patients with a disease or syndrome based on their genotype. The most extreme of obvious examples of this are diseases caused by single gene defects. The ability accurately to subclassify based on common genetic variation is less clear.
• Targeting of specific drugs for patients with specific gene variants. This is most advanced in the field of cancer (usually targeting somatic changes in cancers) and increasingly in the field of the pharmacogenetics of safety (i.e. unwanted drug effects).
Consequences of these expectations include: smaller clinical trial programmes with well-defined patient groups (based on phenotypic and genotypic characterisation), better understanding of the pharmacokinetics and dynamics according to genetic variation, and improved monitoring of adverse events after marketing.
New drug development proceeds thus:
• Idea or hypothesis. ‘This protein causes this disease/these effects which I could stop by affecting protein function.’
• Design and synthesis of substances. ‘This molecule produces the wanted effect on protein function and has the physico-chemical characteristics that make it a potential medicine.’
• Studies on tissues and whole animal (preclinical studies). ‘When I test it in appropriate models it does what I expect and that allows me to believe it would do the same in humans.’
• Studies in humans (clinical studies) (see Ch. 4). ‘Initially I want to know whether the molecule has drug-like properties in terms of its kinetics. I then want to know that it does what I need it to do in terms of the effect on disease.’
• Granting of an official licence to make therapeutic claims and to sell (see Ch. 6). ‘Is my medicine better than than placebo? Does it do more than existing medicines and is it well tolerated.’
• Post-licensing (marketing) studies of safety and comparisons with other medicines. ‘Now many thousands of patients have taken it, am I still sure that it is safe.’
The (critical) phase of progress from the laboratory to humans is often termed translational science or experimental medicine. It was defined as ‘the application of biomedical research (pre-clinical and clinical), conducted to support drug development, which aids in the identification of the appropriate patient for treatment (patient selection), the correct dose and schedule to be tested in the clinic (dosing regimen) and the best disease in which to test a potential agent’.4
It will be obvious from the account that follows that drug development is an extremely arduous, highly technical and enormously expensive operation. Successful developments (1% of compounds that proceed to full test eventually become licensed medicines) must carry the cost of the failures (99%).5 It is also obvious that such programmes are likely to be carried to completion only when the organisations and the individuals within them are motivated overall by the challenge to succeed and to serve society, as well as to make money. A previous edition of this chapter included a quote from a paper I wrote from my time in academia and I leave it here:
Let us get one thing straight: the drug industry works within a system that demands it makes a profit to satisfy shareholders. Indeed, it has a fiduciary6 duty to do so. The best way to make a lot of money is to invent a drug that produces a dramatically beneficial clinical effect, is far more effective than existing options, and has few unwanted effects. Unfortunately most drugs fall short of this ideal.7
Techniques of discovery
(See Fig. 3.1)
Fig. 3.1 Drug discovery sources in context. Different types of chemical compounds (top left) are tested against bioassays that are relevant to therapeutic targets, which are derived from several possible sources of information (right). The initial lead compounds discovered by the screening process are optimised by analogue synthesis and tested for appropriate pharmacokinetic properties. The candidate compounds then enter the development process involving regulatory toxicology studies and clinical trials.
The newer technologies, the impact of which has yet to be fully felt, include the following:
Molecular modelling and structural biology
aided by three-dimensional computer graphics (including virtual reality) allows the design of structures based on new and known molecules to enhance their desired, and to eliminate their undesired, properties to create highly selective targeted compounds. In principle all molecular structures capable of binding to a single high-affinity site can be modelled.
High throughput screening
allows the screening of millions of compounds against a single target or a cell-based screen to determine activity against the target. Traditionally these are large robotic screens but newer technologies, including use of small molecules using coding tags, allow miniaturisation of the process. The quality of the ‘hit’ which is the starting point for medicinal chemistry ‘lead optimisation’, depends on the quality of the molecules in the compound collection and the nature of the biochemical target used for the screen.
Fragments
If the crystal structure of the protein target is known it is possible to screen small fragments of potential drugs to find those that bind and where they bind. It is then possible to construct a drug by adding fragments.
Proteins as medicines: biotechnology
The targets of most drugs are proteins (cell receptors, enzymes) and it is only lack of technology that has hitherto prevented the exploitation of proteins (and peptides) as medicines. This technology is now available and some of the most successful new medicines of the last few years have been biological – antibodies or petides. The practical limitations are that (1) they need to be injected, as they are digested when swallowed and (2) they target soluble factors and targets on the cell membrane but are generally unable to target intracellular proteins. However, these limitations are offset by their high degree of specificity, their often very long half-life (for antibodies) that means that the medicine may be given by monthly injections, and the more predictable toxicity when compared to the rather unpredictable effect of classical small molecule drugs (the usual ‘white pills’). Biotechnology involves the use of recombinant DNA technology/genetic engineering to clone and express human genes, for example in microbial (Escherichia coli or yeast) cells so that they manufacture proteins. Such techniques can deliver hormones and autacoids in commercial amounts (such as insulin and growth hormone, erythropoietins, cell growth factors and plasminogen activators, interferons, vaccines and – probably most important – antibodies).
Transgenic animals (that breed true for the gene) are also used as models for human disease as well as for production of medicines.
Antisense approaches
Nucleic acid approaches are being developed to silence gene expression and therefore reduce the expression of culprit proteins. There are various different ways of achieving this including antisense, locked nucleic acids, small interfering RNAs, and interfering with microRNAs. The problems are (1) delivery – they are injectables, (2) the distribution in the body – mainly liver and kidney – and (3) the difficulty in getting the nucleic acid into cells. Nonetheless, where the treatment aim is local (intraocular injection or inhalation to the lung), or where a liver effect is desired, it is clear that this approach works and provides a potentially attractive approach to targeting those proteins or protein–protein interactions that are intractable to a small molecule, peptide or antibody approach.
Gene therapy
of human genetic disorders is ‘a strategy in which nucleic acid, usually in the form of DNA, is administered to modify the genetic repertoire for therapeutic purposes’, e.g. in diseases caused by single gene defects. Once again significant problems remain, in particular the methods of delivery and the safety and efficiency of the vectors used to deliver the genes. So far success has been seen in the treatment of certain rare haemopoetic disorders and genetic immunodeficiency states where the gene transfer can be done ex vivo and the modified cells reinjected.
Stem cells
Stem cells are impacting drug discovery as they potentially provide a source of human cells, or even disease-specific human cells that can be used for screening and safety testing. Stem cell therapy is a reality in the form of bone marrow transplants but in other areas is still at a very early stage. However, the promise is of regenerative treatments based either on stem cell replacement or chemical stimulation of endogenous stem cells.
Immunopharmacology
Understanding of the molecular basis of immune responses has allowed the definition of mechanisms by which cellular function is altered by a legion of local hormones or autacoids in, for example, infections, cancer, autoimmune diseases, organ transplant rejection. These processes present targets for therapeutic intervention – hence the rise of immunopharmacology.
Older approaches
to the discovery of new medicines that continue in use include:
• Animal models of human disease or an aspect of it of varying relevance to humans. It is always the case that the animal model is never a true model of human disease and can only model parts of the disease process. The trend in industry is to move fast to the clinic and not to rely too heavily on animal models.
• Natural products: modern technology for screening has revived interest and intensified the search. Multinational pharmaceutical companies now scour the world for leads from microorganisms (in soil or sewage or even from insects entombed in amber 40 million years ago), fungi, plants and animals. Developing countries in the tropics (with their luxuriant natural resources) are prominent targets in this search and have justly complained of exploitation (‘gene robbery’). Many now require formal profit-sharing agreements to allow such searches. Natural products have been particularly successful for finding antibiotics as evolution has done over a much longer time period what medicinal chemists struggle to do. The problem with natural product drug discovery is often that identifying the precise active ingredient is hard and the molecules usually cannot easily be synthesised.
• Traditional medicine, which is being studied for possible leads to usefully active compounds. This is particularly true in China where traditional medicines are being re-evaluated for effects. The most notable example in recent years is the rediscovery of artemisinin for malaria treatment.
• Modifications of the structures of known drugs: these are obviously likely to produce more agents with similar basic properties, but may deliver worthwhile improvements. It is in this area that the ‘me too’ and ‘me again’ drugs are developed. However, such approaches are very unlikely to be commercially successful in a world that rightly demands true advances in patient care as a prerequisite for making profits and charging high costs to cover the price of innovative discovery.
• Random screening of synthesised and natural products.
• New uses for drugs already in general use as a result of intelligent observation and serendipity,8 or advancing knowledge of molecular mechanisms, e.g. aspirin for antithrombotic effect. Once a good drug is on the market new uses are often discovered. A recent example is rituximab, a monocloncal antibody that kills B cells. Initially developed for the treatment of B cell lymphoma it was found to be effective for suppressing B cell autoimmunity in diseases such as rheumatoid arthritis.
Drug quality
It is easy for an investigator or prescriber, interested in pharmacology, toxicology and therapeutics, to forget the fundamental importance of chemical and pharmaceutical aspects. An impure, unstable drug or formulation is useless. Pure drugs that remain pure drugs after 5 years of storage in hot, damp climates are vital to therapeutics. The record of manufacturers in providing this is impressive. Much of the early work in drug discovery is spent trying to identify the right molecule with the appropriate physical and chemical properties to make it reliable as a medicine.
Studies in animals9
Generally, the following are undertaken:
Pharmacodynamics
– to investigate the actions relating to the proposed therapeutic use. In addition, there is a need to investigate potential undesirable pharmacodynamic effects of the substance on physiological functions.
Pharmacokinetics
– the study of the fate of the active substance and its metabolites within the organism (absorption, distribution, metabolism and excretion of these substances). The programme should be designed to allow comparison and extrapolation between animal and human.
Toxicology
– to reveal physiological and/or histopathological changes induced by the drug, and to determine how these changes relate to dose.10 These involve:
• Acute toxicity: single-dose studies that allow qualitative and quantitative assessment of toxic reactions.
• Chronic and subchronic toxicity: repeat-dose studies to characterise the toxicological profile of a drug following repeated administration. This includes the identification of potential target organs and exposure–response relationships, and may include the potential for reversibility of effects.
Generally, it is desirable that tests be performed in two relevant species, based on the pharmacokinetic profile, one a rodent and one a non-rodent. The duration of the studies depends on the conditions of clinical use and is defined by Regulatory Agencies (Tables 3.1 and 3.2).
Table 3.1 Single and repeated dose toxicity requirements to support studies in healthy normal volunteers (Phase 1) and in patients (Phase 2) in the European Union (EU), and Phases 1, 2 and 3 in the USA and Japan1
|
Minimum duration of repeated-dose toxicity studies |
||
|
Duration of clinical trial |
Rodents |
Non-rodents |
|
Single dose |
2 weeks2 |
2 weeks |
|
Up to 2 weeks |
2 weeks |
2 weeks |
|
Up to 1 month |
1 month |
1 month |
|
Up to 3 months |
3 months |
3 months |
|
Up to 6 months |
6 months |
6 months |
|
> 6 months |
6 months |
Chronic3 |
1 In Japan, if there are no Phase 2 clinical trials of equivalent duration to the planned Phase 3 trials, conduct of longer-duration toxicity studies is recommended as given in Table 3.2.
2 In the USA, specially designed single-dose studies with extended examinations can support single-dose clinical studies.
3 Regulatory authorities may request a 12-month study or accept a 6-month study, determined on a case-by-case basis.
Table 3.2 Repeated-dose toxicity requirements to support Phase 3 studies in the EU, and marketing in all regions1
|
Minimum duration of repeated-dose toxicity studies |
||
|
Duration of clinical trial |
Rodents |
Non-rodents |
|
Up to 2 weeks |
1 month |
1 month |
|
Up to 1 month |
3 months |
3 months |
|
Up to 3 months |
6 months |
3 months |
|
> 3 months |
6 months |
Chronic2 |
1 When a chronic non-rodent study is recommended if clinical use more than 1 month.
2 Regulatory authorities may request a 12-month study or accept a 6-month study, determined on a case-by-case basis.
Genotoxicity
– to reveal the changes that a drug may cause in the genetic material of individuals or cells. Mutagenic substances present a hazard to health because exposure carries the risk of inducing germline mutation (with the possibility of inherited disorders) and somatic mutations (including those leading to cancer). A standard battery of investigations includes: a test for gene mutation in bacteria (e.g. the Ames test); an in vitro test with cytogenetic evaluation of chromosomal damage with mammalian cells or an in vitro mouse lymphoma thymidine kinase (tk) assay; an in vivo test for chromosomal damage using rodent haematopoietic cells (e.g. the mouse micronucleus test).
Carcinogenicity
– to reveal carcinogenic effects. These studies are performed for any medicinal product if its expected clinical use is prolonged (about 6 months), either continuously or repeatedly. These studies are also recommended if there is concern about their carcinogenic potential, e.g. from a product of the same class or similar structure, or from evidence in repeated-dose toxicity studies. Studies with unequivocally genotoxic compounds are not needed, as they are presumed to be trans-species carcinogens, implying a hazard to humans.
Reproductive and developmental toxicity
– these tests study effects on adult male or female reproductive function, toxic and teratogenic effects at all stages of development from conception to sexual maturity and latent effects, when the medicinal product under investigation has been administered to the female during pregnancy. Embryo/fetal toxicity studies are normally conducted on two mammalian species, one a non-rodent. If the metabolism of a drug in particular species is known to be similar to that in humans, it is usual to include this species. Studies in juvenile animals may also be required prior to developing drugs for use in children.
Local tolerance
– to ascertain whether drugs are tolerated at sites in the body at which they may come into contact in clinical use. The testing strategy is such that any mechanical effects of administration or purely physicochemical actions of the product can be distinguished from toxicological or pharmacodynamic ones.
Biotechnology-derived pharmaceuticals
– present a special case and the standard regimen of toxicology studies is not appropriate. The choice of species used depends on the expression of the relevant receptor. If no suitable species exists, homologous proteins or transgenic animals expressing the human receptor may be studied and additional immunological studies are required. The study of biopharmaceutical safety provides challenges different from small molecules. Whereas the promiscuity of small molecules can lead to unexpected scaffold-related toxicity, this is usually not the case for biopharmaceuticals. But biopharmaceuticals may produce very different kinetics, binding and immunological effects in different species and therefore predictions of receptor occupancy and detailed analysis of immunological differences between species become of key importance.
Ethics and legislation
Controversy surrounding the use of animals in scientific research is not new. The renowned Islamic physician Avicenna (980–1037) was aware of the issues for he held that ‘the experimentation must be done with the human body, for testing a drug on a lion or a horse might not prove anything about its effect on man’.11 Leonardo da Vinci (1452–1519) predicted that one day experimentation on animals would be judged a crime, but Descartes12 asserted that ‘Animals do not speak, therefore they do not think, therefore they do not feel’. Later, Jeremy Bentham (1748–1832), the founding father of utilitarian philosophy, asked of animals: ‘The question is not, Can they reason? nor Can they talk? but Can they suffer?’.
In our present world, billions of animals are raised to provide food and many to be used for scientific experiments. The arguments that evolve from this activity centre on the extent to which non-human animals can be respected as sentient beings of moral worth, albeit with differences between species. In recent years, a boisterous animal rights movement, asserting the moral status of animals, has challenged their use as experimental subjects.13 Mainstream medical and scientific opinion around the world accepts that animal research continues to be justified, subject to important protections. This position is based on the insight that research involving animals has contributed hugely to advances in biological knowledge that have in turn allowed modern therapeutics to improve human morbidity and mortality. However, each experiment must be justified and its results must be expected to deliver insight into safety or efficacy. Animal models do contribute to the understanding of human physiology and disease because we share so many biological characteristics and a medicine when introduced into the organism is exposed to a vast array of conditions that we do not fully understand and are unable to reproduce outside the living body. The study of a drug in the whole organism remains an essential step in the process of discovery and development of medicines.
Safety testing in animals is at present the only reliable way to evaluate risks before undertaking clinical trials of potentially useful medicines in humans. The investigation of reproductive effects and potential carcinogenicity would not be undertaken in humans for both ethical and practical reasons. Animal testing eliminates many unsafe test materials before clinical testing on humans, and minimises the risk of possible adverse effects when people are exposed to potential new medicines. In other words, experiments in animal models provide a critical safety check on candidate drugs; potentially hazardous or ineffective drugs can be eliminated and for those drugs that do progress to clinical trials, target organs identified in animal studies can be monitored.
Animal research has contributed to virtually every area of medical research, and almost all best known drug and surgical treatments of the past and present owe their origins in some way to evidence from animals. The antibacterial effectiveness of penicillin was proved in tests on mice. Insulin came about because of research on rabbits and dogs in the 1920s. Poliomyelitis epidemics, which until the 1950s killed and paralysed millions of children, were consigned to history by vaccines resulting from studies on a range of laboratory animals, including monkeys. Major heart surgery, such as coronary artery bypass grafts and heart transplants, was developed through research on dogs and pigs. The BCG vaccine for tuberculosis was developed through research on rats and mice. Meningitis due to Haemophilus influenzae type b, formerly common especially in children, is now almost unknown in the UK because of a vaccine developed through work on mice and rabbits. Almost all of the highly effective drug treatments we currently use were developed using animals: β-adrenoceptor blockers, angiotensin-converting enzyme inhibitors, cytotoxics, analgesics, psychotropics, and so on.
Given this evidence, there is broad public support for the position that experiments on animals are a regrettable necessity that should be limited to what is deemed essential while alternatives are developed. In the UK, for example, this reservation is expressed in progressively more stringent legislation. The Animals (Scientific Procedures) Act 1986 makes it an offence to carry out any scientific procedure on animals except under licence, the requirements of which include that:
• Animals are only used as a last resort.
• Every practical step is taken to avoid distress or suffering.
• The smallest possible number of animals is used.
• The potential benefits have to be weighed against the cost to the animals; the simplest or least sentient species is used.
• The work is realistic and achievable, and the programme designed in the way most likely to produce satisfactory results.
• The results must impact the decision-making process for discovery or development of the medicine.
Despite the continued necessity of animal studies in drug discovery and development there is now a very clear aim to move medicines into the clinic as soon as safely possible. Detailed clinical experimentation is often a better way to sort out questions related to effects on human biology and pharmacokinetics.
Safety prediction
Knowledge of the mode of action of a potential new drug obviously greatly enhances prediction from animal studies of what will happen in humans. Whenever practicable, such knowledge should be obtained; sometimes this is quite easy, but sometimes it is impossible. Many drugs have been introduced safely without such knowledge, the later acquisition of which has not always made an important difference to their use (e.g. antimicrobials). Pharmacological studies are integrated with those of the toxicologist to build up a picture of the undesired as well as the desired drug effects.
In pharmacological testing, the investigators know what they are looking for and choose the experiments to gain their objectives.
In toxicological testing, the investigators have a less clear idea of what they are looking for; they are screening for risk, unexpected as well as predicted, and certain major routines must be done. Toxicity testing is therefore liable to become a routine to meet regulatory requirements to a greater extent than the pharmacological studies. The predictive value of special toxicology (above) is particularly controversial. All drugs are poisons if enough is given, and the task of the toxicologist is to find out whether, where and how a compound acts as a poison to animals, and to give an opinion on the significance of the data in relation to risks likely to be run by human beings. This will remain a nearly impossible task until molecular explanations of all effects can be provided.
Toxicologists are in an unenviable position. When a useful drug is safely introduced, they are considered to have done no more than their duty. When an accident occurs, they are invited to explain how this failure of prediction came about. When they predict that a chemical is unsafe in a major way for humans, this prediction is never tested. The easiest decision to make in drug discovery is to stop a project, and it is the only decision that can never be shown to be wrong. However, it is also a decision that may deny the world a new and effective medicine.
Orphan drugs and diseases
A free-market economy is liable to leave untreated both rare diseases, e.g. some cancers (in all countries), and some common diseases, e.g. parasitic infections (in poor countries).
In order to stimulate drug discovery and development in rare diseases, legislation in some countries has provided specific incentives to industry to develop medicines for ‘orphan diseases’. Interestingly, many rare diseases are monogenic and the cause is clear. This, unlike most common diseases, means that the drug target is absolutely clear. In view of the greater certainty around cause, the smaller clinical trials and the more receptive regulatory environment, several pharmaceutical companies are beginning to work more assiduously in this area. It is also the case that some rare diseases give significant insights into common diseases and how to approach them.
Guide to further reading
Dollery C.T. Beyond genomics. Clin. Pharmacol. Ther.. 2007;82(2):366–370.
Evans W.E., Relling M.V. Moving towards individualized medicine with pharmacogenomics. Nature. 2004;429:464–468.
Garattini S., Chalmers I. Patients and the public deserve big changes in the evaluation of drugs. Br. Med. J.. 2009;338:804–806.
Lean M.E.J., Mann J.I., Hoek J.A., et al. Translational research. Br. Med. J.. 2008;337:705–706.
Lesko L.J. Personalized medicine: elusive dream or imminent reality? Clin. Pharmacol. Ther.. 2007;81(6):807–816.
Meyer U.A. Pharmacogenetics – five decades of therapeutic lessons from genetic diversity. Nat. Rev. Genet.. 2004;5(9):669–676.
Pound P., Ebrahim S., Sandercock P., et al. Where is the evidence that animal research benefits humans? Br. Med. J.. 2004;328:514–517.
Vallance P., Levick M. Drug discovery and development in the age of molecular medicine. Clin. Pharmacol. Ther.. 2007;82(2):363–365.
Weinshilboum R., Wang L. Pharmacogenomics: bench to bedside. Nat. Rev. Drug Discov.. 2004;3(9):739–748.
1 Paul Ehrlich (1845–1915), a German scientist, who pioneered the scientific approach to drug discovery. The 606th organic arsenical that he tested against spirochaetes (in animals) became a successful medicine (Salvarsan 1910); it and a minor variant were used against syphilis until superseded by penicillin in 1945.
2 Paracelsus (1493–1541) was a controversial figure who has been portrayed as both ignorant and superstitious. He had no medical degree; he burned the classical medical works (Galen, Avicenna) before his lectures in Basle (Switzerland) and had to leave the city following a dispute about fees with a prominent churchman. He died in Salzburg (Austria), either as a result of a drunken debauch or because he was thrown down a steep incline by ‘hitmen’ employed by jealous local physicians. But he was right about the dose.
3 Culliton B J 1994 Nature Medicine 1:1 [editorial].
4 Johnstone D 2006 pA2 online (E-journal of the British Pharmacological Society) 4(2). Available at: http://www.pa2online.org/articles/article.
5 The cost of development of a new chemical entity (NCE) (a novel molecule not previously tested in humans) from synthesis to market (general clinical use) is estimated at over $1.6 billion; the process may take as long as 15 years (including up to 10 years for clinical studies), which is relevant to duration of patent life and so to ultimate profitability; if the developer does not see profit at the end of the process, the investment will not be made. The drug may fail at any stage, including the ultimate, i.e. at the official regulatory body, after all the development costs have been incurred. It may also fail (due to adverse effects) within the first year after marketing, which constitutes a catastrophe (in reputation and finance) for the developer as well as for some of the patients. Pirated copies of full regulatory dossiers have substantial black market value to competitor companies, who have used them to leapfrog the original developer to obtain a licence for their unresearched copied molecule. Dossiers may be enormous, even a million pages or the electronic equivalent, the latter being very convenient as it allows instant searching.
6 Held or given in trust (OED).
7 Vallance P 2005 Developing an open relationship with the drug industry. Lancet 366:1062–1064.
8 Serendipity is the faculty of making fortunate discoveries by general sagacity or by accident; the word derives from a fairytale about three princes of Serendip (Sri Lanka) who had this happy faculty.
9 Mouse, rat, hamster, guinea-pig, rabbit, cat, dog, and sometimes monkey are used (but not all for any one drug). Non-clinical (pharmacotoxicological) studies must be carried out in conformity with the provisions of internationally agreed standards known as Good Laboratory Practice (GLP). In Europe, regulations ensure that all tests on animals are conducted in accordance with Council Directive 86/609/EEC. Certain studies in animals can be substituted by validated in vitro tests provided that the test results are of comparable quality and usefulness for the purpose of safety evaluation. The pharmacological and toxicological tests must demonstrate the potential toxicity of the product and any dangerous or undesirable toxic effects that may occur under the proposed conditions of use in human beings; these should be evaluated in relation to the pathological condition concerned. The studies must also demonstrate the pharmacological properties of the product, in both qualitative and quantitative relationship to the proposed use in human beings.
10 Details can be found at: http://www.ema.europa.eu/.
11 Bull J P 1959 The historical development of clinical therapeutic trials. Journal of Chronic Diseases 10:218–248.
12 René Descartes (1596–1650), French philosopher, mathematician and scientist, acknowledged as one of the chief architects of the modern age.
13 The publication of Animal Liberation (New York: New York Review/Random House) by Peter Singer in 1975 is widely regarded as having provided its moral foundation.